Geosynthetic Clay Liners (GCLs)
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Form #: 06-224 Guidance Documents Revised: 1/13/23

Geosynthetic Clay Liners (GCLs)

This document provides guidance on design and construction quality assurance information needed for GCL liner designs.

GCLs are factory manufactured hydraulic barriers, typically consisting of sodium bentonite clay or other very low permeability material, sandwiched between geotextiles and/or geomembranes. When GCLs are sandwiched between geotextiles they are held together by needling and/or stitching, and are typically 7 to 10 mm thick when hydrated. Some GCL’s hold the sodium bentonite to a geomembrane with chemical adhesives.

The Department of Environment and Energy believes that in terms of steady flux of water, the GCL is equivalent to two feet of compacted clay liner (CCL) at 1 X 10E
-7 cm/sec permeability. Therefore, an alternate liner design demonstration is not required when a GCL is substituted for the permeability requirement of the CCL component of a composite liner design. Two feet of the compacted base must support the GCL.

NDEE has determined that using a GCL as an alternate liner design described above in landfill construction, constitutes a modification. Modifications must be public noticed for 30 days and may require a modification fee.


Performance data should be provided on material properties and/or studies showing each material’s performance, including all physical properties of the material necessary to evaluate its suitability for the site specific use. Examples include:
  • Bearing capacity of the material and any design features to prevent failure of the material under load.
  • Creep analysis and how the material usage, site design, and/or operation of the site maintain stable slopes. Many of the materials utilize a bonding method to provide structural strength across the GCL. These may be adhesives, stitching, or needle punching. Long-term stability may be highly affected by the type of bonding used in the GCL.
  • Stress-strain data necessary to evaluate any mass or differential settlement which can be expected in the site design.
  • Site specific data for slope stability is preferred, but published data will be acceptable on slopes no steeper than 4:1 (4 ft. horizontal to 1 ft. vertical) or approximately 14 degrees.

Construction Quality Assurance (CQA)

CQA requirements for GCL’s differ from those for a compacted clay liner. Some, but not all, of the considerations to be included in the site CQA plan follow.

GCLs should be kept dry during installation. Installation should not take place during high humidity, rain, or other types of precipitation.

Overlapping of the GCL to form seams should be completed according to manufacturer’s specifications. The seaming procedures and inspections should be part of the CQA Plan. Bentonite may be needed for seaming, depending on the manufacturer’s recommendation. If bentonite is used, the amount must be specified and verified as part of CQA monitoring activities

The GCL should be covered by the fabric membrane liner immediately to protect it from any precipitation that may occur during construction. GCL must be completely protected (no exposure) at the end of each construction day. Equipment travel on the GCL, such as a loader, dozer, scraper, etc. should not be allowed. Manufacturer’s recommendations should be followed. If heavy equipment, as defined in the CQA Plan, is to be used for placement of cover material over the GCL, the equipment must be continuously observed by CQA personnel. Manufacturer’s recommendations on the vertical separation distance between the equipment and GCL must be followed. Initial lifts of refuse placed on the liner system should be monitored so that no material is placed on the liner that could eventually cause a penetration into the GCL.

Subgrade must be compacted to 95% of Standard Proctor dry density and be free of sharp objects larger than one inch maximum in any direction.

The subgrade must be free from any chemicals that can damage or cause the sodium bentonite GCL to lose its double layer characteristics. The subgrade must be moistened with potable water. The subgrade must provide moisture for the first hydration of the GCL but should not be so wet as to leave wheel imprints, which prevent intimate contact between the geomembrane, subgrade, and GCL. Moisture in the geomembrane hot wedge joints will prevent good seals.


  • NDEE Main Number (402) 471-2186
  • NDEE Toll Free Number (877) 253-2603
  • NDEE Hazardous Waste Compliance Assistant (402) 471-8308
  • Email questions to:

NDEE Publications:

Reference list attached

Produced by: Nebraska Department of Environment and Energy, P.O. Box 98922, Lincoln, NE 68509-8922; phone (402) 471-2186. To view this, and other information related to our agency, visit our web site at

Symposium on Testing and Acceptance Criteria for Geosynthetic Clay Liners
Sponsored by:
ASTM Committee DD-35 on Geosynthetics

These will be published as Special Technical Paper’s (STP’s)

  • Swell Measurements of the Clay Component of Geosynthetic Clay Liners – D.B. Narejo
  • Internal Shear Strength of a Geosynthetic Clay Liner – T.D. Stark and H.T. Eid
  • A Comparison of Sample Preparation Methodology in the Evaluation of GCL Permeability – J. Siebken, S. Lucas
  • Tests for Evaluating the Performance of GCLs with Leachate and Other Chemicals – T. Egloffstein
  • Correlation of Quality Control Index Tests of Bentonite with Laboratory Tests of GCL Permeability - J. Siebken, S. Lucas
  • Interface Shear Performance of Different GCLs and Selection of Strength Parameters for Design – R. Hewitt, C. Soydemir, and R. Stulgis
  • Creep Shear Characteristics of Two Types of Needle-Punched, Thermally Locked GCL – J. Siebken, R.H. Swan, Jr., and Z.Yuan
  • Long-Term Internal Shear Strength of a Needle-Punched GCL – R. Trauger, R.H. Swan, Jr., and Z. Yuan
  • Factors Influencing Laboratory Measurements of the Internal and Interface Shear Strength – R. H. Swan, Jr., Z. Yuan and R.C. Bachus
  • Shear Strength Testing for Geosynthetic Clay Liners – R.B. Gilbert, D.E. Daniel, and H. Scranton
  • Evaluation of Hydraulic Compatibility of Partially Hydrated GCLs with Contaminated Liquid – J. Mlynarek
  • Geosynthetic Clay Liners in Alkaline Environments – J.A. McKelvey III
  • Laboratory Demonstration of Geoclay Liner Application in Contaminated Liquids Evacuation – J. Mlynarek and O.G. Vermeersch
  • Initial Hydration Conditions Influence on GCLs Leachate Hydraulic Conductivity – G. Didier and L. Comeaga
  • Measurements of Hydraulic Conductivity Properties of Geosynthetic Clay Liners Using a Flow-Box –D.E. Daniel and S.J. Trautwein
  • Hydraulic Conductivity Testing of GCLs in Flexible-Wall Permeaters – D.E. Daniel and J.J. Bowders
  • Rapid Measurement of Hydraulic Conductivity of Geosynthetic Clay Liners Using a Constant Volume Procedure--C.H. Benson and L. Blotz, and S.J. Trautwein
  • What is the Acceptable Shear Strength of a Geosynthetic Clay Liner? – U.W. Cowland
  • Manufacturing Quality Control of GCLs and Design Criteria - - Kvon Maubeuge
  • Specification for GCL – Available Product or Performance? - - J. B. Kirsch and N. Paruvakat and M.J. Cieslik
  • Investigation of Cover Soil Properties on Geosynthetic Clay Liner Performance – P.J. Fox and D. J. DeBattista
  1. Bachus, R., Schmertmann, G. and Swan, R. (1994) “Shear Strength Considerations of Geosynthetic Clay Liners”, GRI-7 Conference on “Geosynthetic Liner Systems, IAFI Publ., St. Paul Minnesota.
  2. Boardman, B.T. and Daniel, D.E. (1996) “Hydraulic Conductivity of Desiccated Geosynthetic Clay Liners”, Journal of Geotechnical Engineering, Vol. 123, No. 3, pp 204-208.
  3. Boardman, B.T., (1993), “The Potential Use of Geosynthetic Clay Liners as Final Covers in Arid Regions”, M.S. Thesis, University of Texas, Austin, Texas.
  4. Byrne, R.J. Kendall, J. and Brown, S. (1992) “Cause and Mechanism of Failure of Landfill B-19, Phase 1a, Kettleman Hills Facility, Kettelman City”, Proc. ASCE Conf. on “Stability and Performance of Slopes and embankments II”, Berkeley, CA, pp. 1-23.
  5. Cooley, B.H. and Daniel, D.E. (1995) “Seam Performance of Overlapped Geosynthetic Clay Liners”, Geosynthetics ’95 Conference Proceedings, Industrial Fabrics Association International, St. Paul, MN, pp. 691-705.
  6. Daniel, D.E. and Boardman, B.T. (1993) “Report on Workshop on Geosynthetic Clay Liners”, U.S. Environmental Protection Agency, EPA/600/R-93/171, August 1993.
  7. Daniel, D.E. Bowders, J.J. and Gilbert, R.B. (1996a) “Laboratory Hydraulic Conductivity Testing of GCLs in Flexible-Wall Permeameters”, Testing and Acceptance Criteria for Geosynthetic Clay Liners, ASTM STP 1308, L.W. Well (Ed), American Society for Testing and Materials, Philadelphia, at press.
  8. Daniel, D.E. and Koerner, R.M., (1993) “Quality Assurance and Quality Control for Waste Containment Facilities”, USEPA, EPA/600/R-93/182, September 1993.
  9. Daniel, D.E., Shan, H-Y and Anderson, J.D., (1993) “Effects of Partial Wetting on the Performance of the Bentonite Component of a Geosynthetic Clay Liner”, Proceedings, Geosynthetics ’93, Vancouver, B.C., IFAI Publ., pp 1483-1496.
  10. Daniel, D.E. Trautwein, S.J. and Goswami, P.K. (1996b) “Measurement of Hydraulic Properties of Geosynthetic Clay Liners Using a Flow Box”, Testing and Acceptance Criteria for Geosynthetic Clay Liners, ASTM STP 1308, L.W. Well (Ed), American Society for Testing and Materials, Philadelhpia, at press.
  11. Daniel, D.E., (1993) “Geosynthetic Clay Liners (GCLs) in Landfill Covers”, Proceedings SWANA Conference, San Jose, CA.
  12. Estornell, P. and D.E. Daniel (1992) “Hydraulic Conductivity of Three Geosynthetic Clay Liners”, Journal of Geotechnical Engineering, Vol. 118, NO. 10, pp. 1592-1606.
  13. Fahim, A. and Koerner, R.M. (1993) “A Survey of State Municipal Solid Waste (MSW) Liner and Cover Systems”, GRI Report #11, August 10, 1993.
  14. Goldman, L. J., Greenfield, L. I., Damle, A.S. Kingsbum, G.L., Northein, CM.M. and Truesdale, R.S. (1998) “Design Construction and Evaluation of Clay Liners for Waste Management Facilities”, EPA/530-SW-86-007-F. Cincinnati, OH, November.
  15. Harpur, W.A., Wilson-Fahmy, R.F. and Koerner, R.M. (1993) “Evaluation of the Contact Between Geosynthetic Clay Liners and Geomembranes in Terms of Transmissivity”, Proceedings 7th GRI Conference on Geosynthetic Liners Systems: Innovations, Concerns and Design, IFAI, St. Paul, MN pp. 138-149.
  16. Hewit,- R.D. and Daniel, D.E. (1996) “Hydraulic Conductivity of Geosynthetic Clay Liners Subjected to Freeze-Thaw”, Journal of Geotechnical Engineering, in review.
  17. Kim, W.H. and D.E. Daniel (1992) “Effects of Freezing on the Hydraulic Conductivity of a Compacted Clay” Journal of Geotechnical Engineering, Vol. 118, No. 7, pp. 1083-1097.
  18. Koerner, R.M. and Narejo, D., “On the Bearing Capacity of Hydrated GCLs”, submitted to ASCE, Journal of Geotechnical Engineering Division, February, 1994.
  19. LaGatta, M.D. Boardman, B.T., Daniel, D.E. and Cooley, B.H. (1996), “Geosynthetic Clay Liners Subjected to Differential Settlement, Journal of Geotechnical Engineering, in review.
  20. LaGatta, M.D. (1983) “Hydraulic Conductivity Tests on Geosynthetic Clay Liners Subjected to Differential Settlement”, M.S. Thesis, University of Texas, Austin, Texas, 1992, (also see Landfill and Surface Impoundment Performance Evaluation Manual, U.S. EPA. SW-869, Technical Resource Document, Cincinnati, OH, April.
  21. Rogowski, A.S. (1990) “Relationship of Laboratory and Field Determined Hydraulic Conductivity in Compacted Clay Liners, “EPA/600/2-90/025, Cincinnati, OH, June.
  22. U.S.EPA (1986) “Saturated Hydraulic Conductivity, Saturated Leachate Conductivity and Intrinsic Permeability, EPA Method 9100 /Cincinnati, OH.